The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Moving Picture Experts Group (MPEG) and Video Coding Experts Group (VCEG) have developed an improved and excellent video compression technology over the existing MPEG-4 Part 2 and H.263 standards. The new standard is called H.264/AVC (Advanced Video Coding) and was released simultaneously as MPEG-4 Part 10 AVC and ITU-T Recommendation H.264. The H.264/AVC (hereinafter referred to as ‘H.264’) can reduce the number of bits of encoded data by performing intra prediction/inter prediction in units of macroblocks each having various types of subblocks to generate a residual signal, transforming and quantizing the generated residual signal, and then encoding the transformed and quantized residual signal.
A video encoding apparatus employing a typical encoding method in units of macroblocks divides an input video into macroblocks, performs prediction with a subblock size which the macroblock may have according to an inter mode or an intra mode, for each macroblock to generate a residual block, applying the 4×4 or 8×8 discrete cosine transform (DCT)-based integer transform to the generated residual block to generate a transform coefficient, and quantizes the transform coefficient according to a given quantization parameter (QP). The blocking effects caused by the transform and quantization processes are reduced through loop filtering.
Since typical video compression technologies, such as the H.264, perform encoding in units of 16×16 macroblocks into which a video to be encoded is divided, and also fix the unit of transform at a block size of 4×4 or 8×8, there is a problem that the encoding efficiency is decreased when a video has high correlations between pixels. That is, when there is high correlations between pixels of a video, it may be efficient to perform prediction in units of macroblocks larger than 16×16 sized macroblocks or in units of various types of macroblocks, and thus it may also be efficient to use various transform block sizes other than the 4×4 block size or 8×8 block size as the unit of transform, but typical video compression technologies cannot perform adaptive encoding according to the features of the video because the macroblock size and the transform block size are fixed, which causes a problem of decreasing the encoding efficiency.